Self-healing material also pinpoints damage

A flexible material that automatically repairs damage and also pinpoints where it has been wounded has been developed by US researchers. They say it could eventually prove useful for airplane maintenance.

The material heals itself by releasing a syrupy epoxy, stored underneath its outer polymer surface when this is breached. The epoxy naturally flows into crack or ruptures and sets hard when exposed to UV light.

However, circuitry embedded in the material also reveals exactly where damage has occurred. An electromagnetic antenna, within a portable "wand", can be used to pinpoint damage from up to 1 metre away. This is because the wand induces a current in the embedded circuit when it is intact. When the circuit is damaged this cannot happen and the wand sounds an alarm.

"We're envisioning putting this onto an aircraft wing or door," says Jennifer English, who developed the skin with colleagues at the University of Alabama in the US.

Hard-to-reach

"A technician could wave a wand over it to check for damage," English explains. "This could quickly pick up things a human wouldn't see from hard-to-reach parts."

The material was made by sandwiching together the syrupy epoxy and copper circuitry between several layers of polymer. English says it should be possible to reinforce the material by simply sandwiching more layers together. The epoxy and copper circuitry can also be patterned using an etching technique already used in the electronics industry.

"In aerospace, people like to have a record of wear and damage to structures," says Ian Bond, who works on self-healing materials for space applications (see Spacecraft skin 'heals' itself), "so embedding sensing abilities could be useful."

Health report

The Alabama team's "smart skin" needs some work before it could be used, however. "There's no reason that damage to the skin should reflect damage to underlying structures," he points out. "And I suspect its mechanical strength is quite poor."

Bond adds that giving sensing and healing abilities to composites already used in aircraft wings, instead of developing new materials, might be a better approach. He also points out that the current material will only repair itself in the daytime.

But the Alabama team is already working on a version that heals in response to air, instead of UV light, and which could also reveal the extent of damage suffered.

"This version doesn't tell us much about what occurred," English admits. The sensor can reveal that a location has been damaged, and not if that same location acquires further damage. But she says that materials that reduce in inductance as they sustain more damage could offer real-time health reports.

If you would like to reuse any content from New Scientist, either in print or online, please contact the syndication department first for permission. New Scientist does not own rights to photos, but there are a variety of licensing options available for use of articles and graphics we own the copyright to.